Thermoelectric refrigeration material and method of making the same

Abstract

In a thermoelectric refrigeration material with thermoelectric conversion characteristic, in order to improve crystallinity of a system of bismuth-antimony (Bi-Sb) and thereby to improve the figure of merit Z, bismuth (Bi), antimony (Sb) and silicon monoxide (SiO) are deposited on a substrate at a predetermined rate in a thermally nonequilibrium state by an ICB method so that a thin film crystal having a granular structure including crystal grains of around one micron is obtained. Consequently, the figure of merit Z can be improved by selectively varying the thermal conductivity K which largely depends upon the crystallinity and which is one of elements of the figure of merit Z determining the thermal conversion coefficiency.

We claim: 
     
       1. A thermoelectric refrigeration material having a thermoelectric conversion characteristic and formed by adding silicon monoxide (SiO) to a system of bismuth-antimony (Bi-Sb) at a predetermined rate such that the formed material has a granular crystalline structure containing crystal grains of around one micron. 
     
     
       2. A thermoelectric refrigeration material according to claim 1, wherein the rate at which SiO is added is approximately 2 atomic percentage or below. 
     
     
       3. A thermoelectric refrigeration material according to claim 1, wherein Bi and Sb in the system of Bi-Sb is approximately in the ratio of 88:12. 
     
     
       4. A thermoelectric refrigeration material according to claim 1, wherein the thermoelectric refrigeration material is formed on a substrate in the form of a thin film. 
     
     
       5. A method of making the thermoelectric refrigeration material according to claim 1 comprising a step of depositing bismuth (Bi), antimony (Sb) and silicon monoxide (SiO) on a substrate at a predetermined rate by a thermally nonequilibrium evaporation so that a thin film of the thermoelectric refrigeration material is formed. 
     
     
       6. A method according to claim 5, wherein an ionized cluster beam (ICB) method is employed as the thermally nonequilibrium evaporation. 
     
     
       7. A method according to claim 6, wherein only Bi clusters are ionized. 
     
     
       8. A method according to claim 7, wherein an applied voltage for ionizing the Bi clusters is approximately at 400 volts and a current of approximately 100 milli-amperes is provided for ionizing the Bi clusters. 
     
     
       9. A method according to claim 5, wherein the substrate is a glass plate. 
     
     
       10. A method according to claim 5, wherein the substrate is maintained at approximately 200° C. during deposition. 
     
     
       11. A method according to claim 5, wherein the vacuum pressure in a deposition area is maintained at an approximate value of 2×10 -6  Torr during deposition 
     
     
       12. A method according to claim 5, wherein an amount of SiO added is adjusted by controlling a calorific value of a heater for heating a pot accommodating SiO. 
     
     
       13. A method according to claim 5, wherein the rate at which SiO is added is approximately 2 atomic percentage or below. 
     
     
       14. A method according to claim 5, wherein Bi and Sb in the system of Bi-Sb is approximately in the ratio of 88:12.